The various fields of forensic expertise include for example toxicology, serology and DNA profiling, trace evidence (e.g. fire debris, glass, paint, gunshot residues), firearms and ballistics, handwriting and document examination, fingerprints, marks and impressions (e.g. tool marks, shoe prints), audio, video and computer analysis, accident investigation, crime scene investigation and forensic pathology. Particularly, the analysis of biological and chemical material has long been of paramount importance in forensic investigations.
Recent technological advances have broadened the scope of such investigations by facilitating analysis of tiny amounts of samples which is called trace evidence and includes the analysis of hair, touched surfaces, fiber, paint, glass, soil, and other particulate matter such as samples containing nucleic acids and proteins. The analysis of DNA from cells by molecular biological methods, such as PCR (polymerase chain reaction), RFLP (restriction fragment length polymorphism), AFLP (amplified fragment length polymorphism) or sequencing permits, for example, the detection of genetic defects or the determination of the HLA (human leukocyte antigen) type as well as other genetic markers, like short tandem repeats (STR) for the identification of individuals.
As the benefits of being able to analyse certain components of biological samples, for example nucleic acids or proteins, have become known, and as the analyses themselves have become more accurate and more accessible, such analyses have become important and frequently used tools, available not only to the medical and veterinary professions, but also in a wide range of other areas, such as in the analysis of forensic materials, pharmaceutical products and intermediates, foods and environmental materials. In many of these areas it is important to maintain the integrity of the molecular structure of a sample while strictly avoiding the contamination and loss of sample.
Responding to a crime scene is a critical step in the scientific investigation of a case. Unless the crime scene response is handled correctly, the investigation may be severely compromised. Crime Scene investigators and crime scene specialists are responsible for identifying, securing, collecting, and preserving evidence which is submitted to the crime laboratory. The investigator's knowledge in crime scene documentation and the variety of methods for the collection and processing of all types of evidence is crucial.
Current procedures for the collection and/or handling of biological and chemical samples employ solid matrices such as cellulose- or cotton-based papers or swabs. After the visual identification the solid matrix is pressed on the surface on which the sample is expected to accept ideally all of the sample material. Adhesion of the sample material is enhanced by different means depending on the structure of the surface on which the sample is to be collected. Same applications prefer the moistening of the solid matrix. Other applications make use of a solid matrix coated with glue, i.e. an adhesive tape. The latter is particularly preferred when the surface is structured, e.g. textiles, due to a higher adhesive force. Another advantage of an adhesive tape is that the sample is not wetted and can be stored dry. Samples collected with a moistened matrix are to be dried before storage to prevent from disintegration such as chemical or biological degradation and to prevent moulding.
The use of an adhesive tape requires a well grounded person. When applying an adhesive tape for the collection of a forensic sample one has to trim the tape according to the desired length using scissors or a knife. The middle part of the tape is used for collecting the sample and the two side parts are used to manually handle the tape. After collecting the sample, the side parts should be cut off saving the middle part for further processing. In order to avoid (cross-) contamination, sterile gloves, scissors and knifes must be changed every time after a single sample has been collected. This procedure is difficult to implement at a crime scene, in any case cumbersome and, thus, bears a high risk for contamination. Furthermore, the flexibility of the tape which is advantageous for the collection from non-even surfaces leads to the undesired sticking of parts of the glued surface to other parts of the tape or to the inner wall surface of a sample tube which is used in the further processing of the sample. This can hamper the subsequent release of the sample from the tape significantly, e.g. when incubating the adhesive tape with lysis buffer to release DNA.
Some disadvantages could be overcome by a development of Helling GmbH (Heidgraben) which offers a device for sample collection which consists of a rod and a rigid or an elastic element at one end of the rod. A double-sided adhesive tape is attached to said element which can be then used to sweep a surface on which a sample is expected. Such devices are called tape lift stubs. Afterwards the double-sided adhesive tape is removed manually or with the aid of a forceps from the element and put into a sample tube. Though this development omitted the cutting of the tape, there are still a significant number of steps which require the touching of the tape by hands or by other external means. Furthermore, the glued surface is limited according to its construction, e.g. 6.6 and 12.7 mm2 as published in Verheil et al. and DeBruin et al. (Forensic Sci. Int., 2011, A protocol for direct and rapid multiplex PCR amplification on forensically relevant samples; Forensic Sci. Int., 2011, Comparison of stubbing and the double swab method for collecting offender epithelial material from a victims skin).
Further devices are known from U.S. 2009/0252820 and U.S. 2009/0209044. These devices employ a sampling head which is detachable from the handle. The detachment mechanism is based on a physical disintegration of the device, i.e. the sampling head is irreversibly torn off the handle. The detachment mechanism bears the risk of cross-contamination when absorbed material bespatters around once the sampling head abruptly tears off. A further disadvantage can be seen in that it is not possible to re-use the handle or, in case of the device according to U.S. 2009/0209044, re-use it without dissembling the whole device, which is not feasible at a crime scene.
A re-use, in turn, appears to be feasible with a device disclosed in U.S. Pat. No. 5,988,002. However, the sampling element is here to be manually grasped taking care not to contact the working portion. Application errors will certainly end in cross-contamination.
In summary, current methods and devices for sample collection from solid surfaces are cumbersome, inefficient, prone to (cross-) contamination and can lead to loss of sample material.
The handling of trace evidence is of particular challenge. Trace evidence is usually not or only hardly visible. The rather big adhesion force makes it sticky towards all kind of surfaces which hampers the handling, e.g. the transfer of the sample from a collection device into a sample tube. As trace evidence is present in tiny quantities, contamination produces a high background even in very small amounts. For example, foreign DNA may completely distort the result of DNA profiling. Due to the above disadvantages, none of the current procedures appear to be useful for handling trace evidence.
Accordingly, it is an object of the present invention to provide a device for collecting a biological and/or chemical sample from a surface exposing said sample material without the above outlined drawbacks.